The present invention relates to a process for preparing amines from sugar alcohols and to the use thereof.
The industrial scale preparation of industrially important aminoalkanols, such as ethanolamine and isopropanolamine, and their conversion products such as ethylenediamine, 1,2-propylenediamine and piperazine, generally proceeds from ethylene oxide or propylene oxide as a C2 or C3 synthesis unit.
For instance, ethanolamine and isopropanolamine are synthesized by reaction of ammonia with ethylene oxide and propylene oxide respectively. As further products, the corresponding dialkanolamines and trialkanolamines are also obtained in this reaction. The ratio of monoalkanolamines to di- and trialkanolamines can be controlled through the use amounts of ammonia relative to alkylene oxide. In order to obtain a higher proportion of trialkanolamines, mono- and dialkanolamines can be recycled into the reactor.
In a further reaction stage, the monoalkanolamines thus obtained can be converted further to ethylenediamine and 1,2-propylenediamine by reaction of hydrogen and ammonia.
1,3-Diaminopropane is obtainable on the industrial scale by reacting ammonia with acrylonitrile and subsequent hydrogenation, and acrylonitrile is generally prepared on the industrial scale by ammoxidizing the C3 unit propene.
As an alternative raw material source to the ethene- or propene-based petrochemical feedstocks mentioned, raw materials based on renewable raw materials may achieve an ever higher status.
Sugar alcohols might gain growing significance in the future.
U.S. Pat. No. 2,016,962 describes the reaction of reducing sugars with hydrogen and an aminating agent (ammonia, primary or secondary amines) in the presence of hydrogenation catalysts (reduced nickel catalysts). The reaction should be performed preferably between 80 and 125° C., since monosaccharides such as glucose decompose in the course of heating. Glucamine and xylamine were obtained from glucose and xylose respectively.
Kelkenberg et al. (H. Kelkenberg, Tenside Surfactants Detergents, 25 (1988), pages 8-13) discloses the synthesis of glucamine by reaction of glucose with amine or ammonia to give the N-glucoside, which is subsequently hydrogenated to glucamine. The reaction is performed in an Ni fixed bed, but the exact reaction conditions are not specified. Excessively severe reaction conditions lead, according to the disclosure, to cleavage reactions and to the formation of ethylenediamine and ethanolamine.
EP-A2-0255033 describes the synthesis of isomaltines from disaccharides by catalytic reductive amination with hydrazine and hydrogen in the presence of Raney nickel catalysts. The reductive amination is performed at 50° C. and a pressure of from 100 to 150 bar.
EP-A2-03990488 likewise discloses the preparation of polyhydroxyamines from disaccharides by reductive amination with hydrazine and hydrogen in the presence of Raney nickel catalysts.
The review article by Fischer et al. (A. Fischer, T. Mallat, A. Baiker, Catalysis Today 37 (1997), pages 167-189) discusses the amination of sugars comprehensively. It is pointed out that the N-glucoside formed as an intermediate in the amination of glucose labile especially in the presence of water and tends to caramelization reactions (Maillard reactions). According to the disclosure, high hydrogenation rates are required in order to reduce the lifetime of the imine (N-glucoside) formed as an intermediate. It is also disclosed that, on the other hand, more severe hydrogenation conditions lead to cleavage products such as ethanolamine and diaminoethane.